The semiconductor industry uses many cleaning solvents. For example, the manufacture of semiconductor components and integrated circuits is carried out using photolithographic processes. Semiconductor substrates are coated with photoresists, developed, and patterned. After these processes, the photoresist and process residues have to be removed. For this purpose, cleaners, solvents, or strippers are used.
Selection of a cleaner involves considering many factors such as volatility, viscosity, acidity, surface tension, environmental, and health and safety. Another important factor is a cleaner's ability to adequately remove one material while leaving other materials unaffected. A major difficulty facing the user is the bewildering array of cleaners available, but a shortage of information to guide the user in selecting a cleaner that has the desired properties. The difficulty is compounded when proprietary concerns prevent disclosure of the details concerning either the cleaner or the application. Often both the chemical supplier and the semiconductor manufacturer are unwilling to disclose material properties because of the possibility of reverse engineering. For example, a semiconductor manufacturer may be unwilling to disclose the composition of an experimental photoresist or a new low-k dielectric. In situations like this, the cleaner manufacturer can offer little guidance to the user in selecting an appropriate cleaner or other solvent.
Determining the optimum cleaning solvent by trial and error is time consuming and expensive. Product literature and technical reports often include an enormous quantity of data, yet lack the ability to predict whether a solvent will work in a given situation. Thermodynamic phase equilibrium calculations are limited in value by their complexity and lack of suitable equilibrium solubility data, particularly for new materials.
In light of considerations such as these, there remains a need for a method of efficiently selecting or producing cleaning solvents. There is a particular need in manufacturing applications where proprietary concerns prevent disclosure of a solvent or solute composition.